selftests/landlock: Test abstract UNIX socket scoping

Add three tests that examine different scenarios for abstract UNIX
socket:

1) scoped_domains: Base tests of the abstract socket scoping mechanism
for a landlocked process, same as the ptrace test.

2) scoped_vs_unscoped: Generates three processes with different domains
and tests if a process with a non-scoped domain can connect to other
processes.

3) outside_socket: Since the socket's creator credentials are used
for scoping sockets, this test examines the cases where the socket's
credentials are different from the process using it.

Move protocol_variant, service_fixture, and sys_gettid() from net_test.c
to common.h, and factor out code into a new set_unix_address() helper.

Signed-off-by: Tahera Fahimi <[e-mail]>
Link: https://lore.kernel.org/r/9321[e-mail]
[mic: Fix commit message, remove useless clang-format tags, move
drop_caps() calls, move and rename variables, rename variants, use more
EXPECT, improve comments, simplify the outside_socket test]
Signed-off-by: Mickaël Salaün <[e-mail]>

tools/testing/selftests/landlock/common.h

···
  * Copyright © 2021 Microsoft Corporation
  */
 
+#include <arpa/inet.h>
 #include <errno.h>
 #include <linux/landlock.h>
 #include <linux/securebits.h>
···
 #include <sys/socket.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
+#include <sys/un.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
···
 	{
 		TH_LOG("Failed to enforce ruleset: %s", strerror(errno));
 	}
+}
+
+struct protocol_variant {
+	int domain;
+	int type;
+};
+
+struct service_fixture {
+	struct protocol_variant protocol;
+	/* port is also stored in ipv4_addr.sin_port or ipv6_addr.sin6_port */
+	unsigned short port;
+	union {
+		struct sockaddr_in ipv4_addr;
+		struct sockaddr_in6 ipv6_addr;
+		struct {
+			struct sockaddr_un unix_addr;
+			socklen_t unix_addr_len;
+		};
+	};
+};
+
+static pid_t __maybe_unused sys_gettid(void)
+{
+	return syscall(__NR_gettid);
+}
+
+static void __maybe_unused set_unix_address(struct service_fixture *const srv,
+					    const unsigned short index)
+{
+	srv->unix_addr.sun_family = AF_UNIX;
+	sprintf(srv->unix_addr.sun_path,
+		"_selftests-landlock-abstract-unix-tid%d-index%d", sys_gettid(),
+		index);
+	srv->unix_addr_len = SUN_LEN(&srv->unix_addr);
+	srv->unix_addr.sun_path[0] = '\0';
 }

tools/testing/selftests/landlock/net_test.c

···
 	TCP_SANDBOX,
 };
 
-struct protocol_variant {
-	int domain;
-	int type;
-};
-
-struct service_fixture {
-	struct protocol_variant protocol;
-	/* port is also stored in ipv4_addr.sin_port or ipv6_addr.sin6_port */
-	unsigned short port;
-	union {
-		struct sockaddr_in ipv4_addr;
-		struct sockaddr_in6 ipv6_addr;
-		struct {
-			struct sockaddr_un unix_addr;
-			socklen_t unix_addr_len;
-		};
-	};
-};
-
-static pid_t sys_gettid(void)
-{
-	return syscall(__NR_gettid);
-}
-
 static int set_service(struct service_fixture *const srv,
 		       const struct protocol_variant prot,
 		       const unsigned short index)
···
 		return 0;
 
 	case AF_UNIX:
-		srv->unix_addr.sun_family = prot.domain;
-		sprintf(srv->unix_addr.sun_path,
-			"_selftests-landlock-net-tid%d-index%d", sys_gettid(),
-			index);
-		srv->unix_addr_len = SUN_LEN(&srv->unix_addr);
-		srv->unix_addr.sun_path[0] = '\0';
+		set_unix_address(srv, index);
 		return 0;
 	}
 	return 1;

tools/testing/selftests/landlock/scoped_abstract_unix_test.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Landlock tests - Abstract UNIX socket
+ *
+ * Copyright © 2024 Tahera Fahimi <[e-mail]>
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/landlock.h>
+#include <sched.h>
+#include <signal.h>
+#include <stddef.h>
+#include <sys/prctl.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "common.h"
+#include "scoped_common.h"
+
+/* Number of pending connections queue to be hold. */
+const short backlog = 10;
+
+static void create_fs_domain(struct __test_metadata *const _metadata)
+{
+	int ruleset_fd;
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_DIR,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	EXPECT_LE(0, ruleset_fd)
+	{
+		TH_LOG("Failed to create a ruleset: %s", strerror(errno));
+	}
+	EXPECT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+	EXPECT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
+FIXTURE(scoped_domains)
+{
+	struct service_fixture stream_address, dgram_address;
+};
+
+#include "scoped_base_variants.h"
+
+FIXTURE_SETUP(scoped_domains)
+{
+	drop_caps(_metadata);
+
+	memset(&self->stream_address, 0, sizeof(self->stream_address));
+	memset(&self->dgram_address, 0, sizeof(self->dgram_address));
+	set_unix_address(&self->stream_address, 0);
+	set_unix_address(&self->dgram_address, 1);
+}
+
+FIXTURE_TEARDOWN(scoped_domains)
+{
+}
+
+/*
+ * Test unix_stream_connect() and unix_may_send() for a child connecting to its
+ * parent, when they have scoped domain or no domain.
+ */
+TEST_F(scoped_domains, connect_to_parent)
+{
+	pid_t child;
+	bool can_connect_to_parent;
+	int status;
+	int pipe_parent[2];
+	int stream_server, dgram_server;
+
+	/*
+	 * can_connect_to_parent is true if a child process can connect to its
+	 * parent process. This depends on the child process not being isolated
+	 * from the parent with a dedicated Landlock domain.
+	 */
+	can_connect_to_parent = !variant->domain_child;
+
+	ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
+	if (variant->domain_both) {
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+		if (!__test_passed(_metadata))
+			return;
+	}
+
+	child = fork();
+	ASSERT_LE(0, child);
+	if (child == 0) {
+		int err;
+		int stream_client, dgram_client;
+		char buf_child;
+
+		EXPECT_EQ(0, close(pipe_parent[1]));
+		if (variant->domain_child)
+			create_scoped_domain(
+				_metadata, LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+		stream_client = socket(AF_UNIX, SOCK_STREAM, 0);
+		ASSERT_LE(0, stream_client);
+		dgram_client = socket(AF_UNIX, SOCK_DGRAM, 0);
+		ASSERT_LE(0, dgram_client);
+
+		/* Waits for the server. */
+		ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
+
+		err = connect(stream_client, &self->stream_address.unix_addr,
+			      self->stream_address.unix_addr_len);
+		if (can_connect_to_parent) {
+			EXPECT_EQ(0, err);
+		} else {
+			EXPECT_EQ(-1, err);
+			EXPECT_EQ(EPERM, errno);
+		}
+		EXPECT_EQ(0, close(stream_client));
+
+		err = connect(dgram_client, &self->dgram_address.unix_addr,
+			      self->dgram_address.unix_addr_len);
+		if (can_connect_to_parent) {
+			EXPECT_EQ(0, err);
+		} else {
+			EXPECT_EQ(-1, err);
+			EXPECT_EQ(EPERM, errno);
+		}
+		EXPECT_EQ(0, close(dgram_client));
+		_exit(_metadata->exit_code);
+		return;
+	}
+	EXPECT_EQ(0, close(pipe_parent[0]));
+	if (variant->domain_parent)
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+	stream_server = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, stream_server);
+	dgram_server = socket(AF_UNIX, SOCK_DGRAM, 0);
+	ASSERT_LE(0, dgram_server);
+	ASSERT_EQ(0, bind(stream_server, &self->stream_address.unix_addr,
+			  self->stream_address.unix_addr_len));
+	ASSERT_EQ(0, bind(dgram_server, &self->dgram_address.unix_addr,
+			  self->dgram_address.unix_addr_len));
+	ASSERT_EQ(0, listen(stream_server, backlog));
+
+	/* Signals to child that the parent is listening. */
+	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
+
+	ASSERT_EQ(child, waitpid(child, &status, 0));
+	EXPECT_EQ(0, close(stream_server));
+	EXPECT_EQ(0, close(dgram_server));
+
+	if (WIFSIGNALED(status) || !WIFEXITED(status) ||
+	    WEXITSTATUS(status) != EXIT_SUCCESS)
+		_metadata->exit_code = KSFT_FAIL;
+}
+
+/*
+ * Test unix_stream_connect() and unix_may_send() for a parent connecting to
+ * its child, when they have scoped domain or no domain.
+ */
+TEST_F(scoped_domains, connect_to_child)
+{
+	pid_t child;
+	bool can_connect_to_child;
+	int err_stream, err_dgram, errno_stream, errno_dgram, status;
+	int pipe_child[2], pipe_parent[2];
+	char buf;
+	int stream_client, dgram_client;
+
+	/*
+	 * can_connect_to_child is true if a parent process can connect to its
+	 * child process. The parent process is not isolated from the child
+	 * with a dedicated Landlock domain.
+	 */
+	can_connect_to_child = !variant->domain_parent;
+
+	ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
+	ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
+	if (variant->domain_both) {
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+		if (!__test_passed(_metadata))
+			return;
+	}
+
+	child = fork();
+	ASSERT_LE(0, child);
+	if (child == 0) {
+		int stream_server, dgram_server;
+
+		EXPECT_EQ(0, close(pipe_parent[1]));
+		EXPECT_EQ(0, close(pipe_child[0]));
+		if (variant->domain_child)
+			create_scoped_domain(
+				_metadata, LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+		/* Waits for the parent to be in a domain, if any. */
+		ASSERT_EQ(1, read(pipe_parent[0], &buf, 1));
+
+		stream_server = socket(AF_UNIX, SOCK_STREAM, 0);
+		ASSERT_LE(0, stream_server);
+		dgram_server = socket(AF_UNIX, SOCK_DGRAM, 0);
+		ASSERT_LE(0, dgram_server);
+		ASSERT_EQ(0,
+			  bind(stream_server, &self->stream_address.unix_addr,
+			       self->stream_address.unix_addr_len));
+		ASSERT_EQ(0, bind(dgram_server, &self->dgram_address.unix_addr,
+				  self->dgram_address.unix_addr_len));
+		ASSERT_EQ(0, listen(stream_server, backlog));
+
+		/* Signals to the parent that child is listening. */
+		ASSERT_EQ(1, write(pipe_child[1], ".", 1));
+
+		/* Waits to connect. */
+		ASSERT_EQ(1, read(pipe_parent[0], &buf, 1));
+		EXPECT_EQ(0, close(stream_server));
+		EXPECT_EQ(0, close(dgram_server));
+		_exit(_metadata->exit_code);
+		return;
+	}
+	EXPECT_EQ(0, close(pipe_child[1]));
+	EXPECT_EQ(0, close(pipe_parent[0]));
+
+	if (variant->domain_parent)
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+	/* Signals that the parent is in a domain, if any. */
+	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
+
+	stream_client = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, stream_client);
+	dgram_client = socket(AF_UNIX, SOCK_DGRAM, 0);
+	ASSERT_LE(0, dgram_client);
+
+	/* Waits for the child to listen */
+	ASSERT_EQ(1, read(pipe_child[0], &buf, 1));
+	err_stream = connect(stream_client, &self->stream_address.unix_addr,
+			     self->stream_address.unix_addr_len);
+	errno_stream = errno;
+	err_dgram = connect(dgram_client, &self->dgram_address.unix_addr,
+			    self->dgram_address.unix_addr_len);
+	errno_dgram = errno;
+	if (can_connect_to_child) {
+		EXPECT_EQ(0, err_stream);
+		EXPECT_EQ(0, err_dgram);
+	} else {
+		EXPECT_EQ(-1, err_stream);
+		EXPECT_EQ(-1, err_dgram);
+		EXPECT_EQ(EPERM, errno_stream);
+		EXPECT_EQ(EPERM, errno_dgram);
+	}
+	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
+	EXPECT_EQ(0, close(stream_client));
+	EXPECT_EQ(0, close(dgram_client));
+
+	ASSERT_EQ(child, waitpid(child, &status, 0));
+	if (WIFSIGNALED(status) || !WIFEXITED(status) ||
+	    WEXITSTATUS(status) != EXIT_SUCCESS)
+		_metadata->exit_code = KSFT_FAIL;
+}
+
+FIXTURE(scoped_vs_unscoped)
+{
+	struct service_fixture parent_stream_address, parent_dgram_address,
+		child_stream_address, child_dgram_address;
+};
+
+#include "scoped_multiple_domain_variants.h"
+
+FIXTURE_SETUP(scoped_vs_unscoped)
+{
+	drop_caps(_metadata);
+
+	memset(&self->parent_stream_address, 0,
+	       sizeof(self->parent_stream_address));
+	set_unix_address(&self->parent_stream_address, 0);
+	memset(&self->parent_dgram_address, 0,
+	       sizeof(self->parent_dgram_address));
+	set_unix_address(&self->parent_dgram_address, 1);
+	memset(&self->child_stream_address, 0,
+	       sizeof(self->child_stream_address));
+	set_unix_address(&self->child_stream_address, 2);
+	memset(&self->child_dgram_address, 0,
+	       sizeof(self->child_dgram_address));
+	set_unix_address(&self->child_dgram_address, 3);
+}
+
+FIXTURE_TEARDOWN(scoped_vs_unscoped)
+{
+}
+
+/*
+ * Test unix_stream_connect and unix_may_send for parent, child and
+ * grand child processes when they can have scoped or non-scoped domains.
+ */
+TEST_F(scoped_vs_unscoped, unix_scoping)
+{
+	pid_t child;
+	int status;
+	bool can_connect_to_parent, can_connect_to_child;
+	int pipe_parent[2];
+	int stream_server_parent, dgram_server_parent;
+
+	can_connect_to_child = (variant->domain_grand_child != SCOPE_SANDBOX);
+	can_connect_to_parent = (can_connect_to_child &&
+				 (variant->domain_children != SCOPE_SANDBOX));
+
+	ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
+
+	if (variant->domain_all == OTHER_SANDBOX)
+		create_fs_domain(_metadata);
+	else if (variant->domain_all == SCOPE_SANDBOX)
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+	child = fork();
+	ASSERT_LE(0, child);
+	if (child == 0) {
+		int stream_server_child, dgram_server_child;
+		int pipe_child[2];
+		pid_t grand_child;
+
+		ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
+
+		if (variant->domain_children == OTHER_SANDBOX)
+			create_fs_domain(_metadata);
+		else if (variant->domain_children == SCOPE_SANDBOX)
+			create_scoped_domain(
+				_metadata, LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+		grand_child = fork();
+		ASSERT_LE(0, grand_child);
+		if (grand_child == 0) {
+			char buf;
+			int stream_err, dgram_err, stream_errno, dgram_errno;
+			int stream_client, dgram_client;
+
+			EXPECT_EQ(0, close(pipe_parent[1]));
+			EXPECT_EQ(0, close(pipe_child[1]));
+
+			if (variant->domain_grand_child == OTHER_SANDBOX)
+				create_fs_domain(_metadata);
+			else if (variant->domain_grand_child == SCOPE_SANDBOX)
+				create_scoped_domain(
+					_metadata,
+					LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+			stream_client = socket(AF_UNIX, SOCK_STREAM, 0);
+			ASSERT_LE(0, stream_client);
+			dgram_client = socket(AF_UNIX, SOCK_DGRAM, 0);
+			ASSERT_LE(0, dgram_client);
+
+			ASSERT_EQ(1, read(pipe_child[0], &buf, 1));
+			stream_err = connect(
+				stream_client,
+				&self->child_stream_address.unix_addr,
+				self->child_stream_address.unix_addr_len);
+			stream_errno = errno;
+			dgram_err = connect(
+				dgram_client,
+				&self->child_dgram_address.unix_addr,
+				self->child_dgram_address.unix_addr_len);
+			dgram_errno = errno;
+			if (can_connect_to_child) {
+				EXPECT_EQ(0, stream_err);
+				EXPECT_EQ(0, dgram_err);
+			} else {
+				EXPECT_EQ(-1, stream_err);
+				EXPECT_EQ(-1, dgram_err);
+				EXPECT_EQ(EPERM, stream_errno);
+				EXPECT_EQ(EPERM, dgram_errno);
+			}
+
+			EXPECT_EQ(0, close(stream_client));
+			stream_client = socket(AF_UNIX, SOCK_STREAM, 0);
+			ASSERT_LE(0, stream_client);
+			/* Datagram sockets can "reconnect". */
+
+			ASSERT_EQ(1, read(pipe_parent[0], &buf, 1));
+			stream_err = connect(
+				stream_client,
+				&self->parent_stream_address.unix_addr,
+				self->parent_stream_address.unix_addr_len);
+			stream_errno = errno;
+			dgram_err = connect(
+				dgram_client,
+				&self->parent_dgram_address.unix_addr,
+				self->parent_dgram_address.unix_addr_len);
+			dgram_errno = errno;
+			if (can_connect_to_parent) {
+				EXPECT_EQ(0, stream_err);
+				EXPECT_EQ(0, dgram_err);
+			} else {
+				EXPECT_EQ(-1, stream_err);
+				EXPECT_EQ(-1, dgram_err);
+				EXPECT_EQ(EPERM, stream_errno);
+				EXPECT_EQ(EPERM, dgram_errno);
+			}
+			EXPECT_EQ(0, close(stream_client));
+			EXPECT_EQ(0, close(dgram_client));
+
+			_exit(_metadata->exit_code);
+			return;
+		}
+		EXPECT_EQ(0, close(pipe_child[0]));
+		if (variant->domain_child == OTHER_SANDBOX)
+			create_fs_domain(_metadata);
+		else if (variant->domain_child == SCOPE_SANDBOX)
+			create_scoped_domain(
+				_metadata, LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+		stream_server_child = socket(AF_UNIX, SOCK_STREAM, 0);
+		ASSERT_LE(0, stream_server_child);
+		dgram_server_child = socket(AF_UNIX, SOCK_DGRAM, 0);
+		ASSERT_LE(0, dgram_server_child);
+
+		ASSERT_EQ(0, bind(stream_server_child,
+				  &self->child_stream_address.unix_addr,
+				  self->child_stream_address.unix_addr_len));
+		ASSERT_EQ(0, bind(dgram_server_child,
+				  &self->child_dgram_address.unix_addr,
+				  self->child_dgram_address.unix_addr_len));
+		ASSERT_EQ(0, listen(stream_server_child, backlog));
+
+		ASSERT_EQ(1, write(pipe_child[1], ".", 1));
+		ASSERT_EQ(grand_child, waitpid(grand_child, &status, 0));
+		EXPECT_EQ(0, close(stream_server_child))
+		EXPECT_EQ(0, close(dgram_server_child));
+		return;
+	}
+	EXPECT_EQ(0, close(pipe_parent[0]));
+
+	if (variant->domain_parent == OTHER_SANDBOX)
+		create_fs_domain(_metadata);
+	else if (variant->domain_parent == SCOPE_SANDBOX)
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+	stream_server_parent = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, stream_server_parent);
+	dgram_server_parent = socket(AF_UNIX, SOCK_DGRAM, 0);
+	ASSERT_LE(0, dgram_server_parent);
+	ASSERT_EQ(0, bind(stream_server_parent,
+			  &self->parent_stream_address.unix_addr,
+			  self->parent_stream_address.unix_addr_len));
+	ASSERT_EQ(0, bind(dgram_server_parent,
+			  &self->parent_dgram_address.unix_addr,
+			  self->parent_dgram_address.unix_addr_len));
+
+	ASSERT_EQ(0, listen(stream_server_parent, backlog));
+
+	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
+	ASSERT_EQ(child, waitpid(child, &status, 0));
+	EXPECT_EQ(0, close(stream_server_parent));
+	EXPECT_EQ(0, close(dgram_server_parent));
+
+	if (WIFSIGNALED(status) || !WIFEXITED(status) ||
+	    WEXITSTATUS(status) != EXIT_SUCCESS)
+		_metadata->exit_code = KSFT_FAIL;
+}
+
+FIXTURE(outside_socket)
+{
+	struct service_fixture address, transit_address;
+};
+
+FIXTURE_VARIANT(outside_socket)
+{
+	const bool child_socket;
+	const int type;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(outside_socket, allow_dgram_child) {
+	/* clang-format on */
+	.child_socket = true,
+	.type = SOCK_DGRAM,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(outside_socket, deny_dgram_server) {
+	/* clang-format on */
+	.child_socket = false,
+	.type = SOCK_DGRAM,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(outside_socket, allow_stream_child) {
+	/* clang-format on */
+	.child_socket = true,
+	.type = SOCK_STREAM,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(outside_socket, deny_stream_server) {
+	/* clang-format on */
+	.child_socket = false,
+	.type = SOCK_STREAM,
+};
+
+FIXTURE_SETUP(outside_socket)
+{
+	drop_caps(_metadata);
+
+	memset(&self->transit_address, 0, sizeof(self->transit_address));
+	set_unix_address(&self->transit_address, 0);
+	memset(&self->address, 0, sizeof(self->address));
+	set_unix_address(&self->address, 1);
+}
+
+FIXTURE_TEARDOWN(outside_socket)
+{
+}
+
+/*
+ * Test unix_stream_connect and unix_may_send for parent and child processes
+ * when connecting socket has different domain than the process using it.
+ */
+TEST_F(outside_socket, socket_with_different_domain)
+{
+	pid_t child;
+	int err, status;
+	int pipe_child[2], pipe_parent[2];
+	char buf_parent;
+	int server_socket;
+
+	ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
+	ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
+
+	child = fork();
+	ASSERT_LE(0, child);
+	if (child == 0) {
+		int client_socket;
+		char buf_child;
+
+		EXPECT_EQ(0, close(pipe_parent[1]));
+		EXPECT_EQ(0, close(pipe_child[0]));
+
+		/* Client always has a domain. */
+		create_scoped_domain(_metadata,
+				     LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+		if (variant->child_socket) {
+			int data_socket, passed_socket, stream_server;
+
+			passed_socket = socket(AF_UNIX, variant->type, 0);
+			ASSERT_LE(0, passed_socket);
+			stream_server = socket(AF_UNIX, SOCK_STREAM, 0);
+			ASSERT_LE(0, stream_server);
+			ASSERT_EQ(0, bind(stream_server,
+					  &self->transit_address.unix_addr,
+					  self->transit_address.unix_addr_len));
+			ASSERT_EQ(0, listen(stream_server, backlog));
+			ASSERT_EQ(1, write(pipe_child[1], ".", 1));
+			data_socket = accept(stream_server, NULL, NULL);
+			ASSERT_LE(0, data_socket);
+			ASSERT_EQ(0, send_fd(data_socket, passed_socket));
+			EXPECT_EQ(0, close(passed_socket));
+			EXPECT_EQ(0, close(stream_server));
+		}
+
+		client_socket = socket(AF_UNIX, variant->type, 0);
+		ASSERT_LE(0, client_socket);
+
+		/* Waits for parent signal for connection. */
+		ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
+		err = connect(client_socket, &self->address.unix_addr,
+			      self->address.unix_addr_len);
+		if (variant->child_socket) {
+			EXPECT_EQ(0, err);
+		} else {
+			EXPECT_EQ(-1, err);
+			EXPECT_EQ(EPERM, errno);
+		}
+		EXPECT_EQ(0, close(client_socket));
+		_exit(_metadata->exit_code);
+		return;
+	}
+	EXPECT_EQ(0, close(pipe_child[1]));
+	EXPECT_EQ(0, close(pipe_parent[0]));
+
+	if (variant->child_socket) {
+		int client_child = socket(AF_UNIX, SOCK_STREAM, 0);
+
+		ASSERT_LE(0, client_child);
+		ASSERT_EQ(1, read(pipe_child[0], &buf_parent, 1));
+		ASSERT_EQ(0, connect(client_child,
+				     &self->transit_address.unix_addr,
+				     self->transit_address.unix_addr_len));
+		server_socket = recv_fd(client_child);
+		EXPECT_EQ(0, close(client_child));
+	} else {
+		server_socket = socket(AF_UNIX, variant->type, 0);
+	}
+	ASSERT_LE(0, server_socket);
+
+	/* Server always has a domain. */
+	create_scoped_domain(_metadata, LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+	ASSERT_EQ(0, bind(server_socket, &self->address.unix_addr,
+			  self->address.unix_addr_len));
+	if (variant->type == SOCK_STREAM)
+		ASSERT_EQ(0, listen(server_socket, backlog));
+
+	/* Signals to child that the parent is listening. */
+	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
+
+	ASSERT_EQ(child, waitpid(child, &status, 0));
+	EXPECT_EQ(0, close(server_socket));
+
+	if (WIFSIGNALED(status) || !WIFEXITED(status) ||
+	    WEXITSTATUS(status) != EXIT_SUCCESS)
+		_metadata->exit_code = KSFT_FAIL;
+}
+
+TEST_HARNESS_MAIN

tools/testing/selftests/landlock/scoped_base_variants.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Landlock scoped_domains variants
+ *
+ * See the hierarchy variants from ptrace_test.c
+ *
+ * Copyright © 2017-2020 Mickaël Salaün <[e-mail]>
+ * Copyright © 2019-2020 ANSSI
+ * Copyright © 2024 Tahera Fahimi <[e-mail]>
+ */
+
+/* clang-format on */
+FIXTURE_VARIANT(scoped_domains)
+{
+	bool domain_both;
+	bool domain_parent;
+	bool domain_child;
+};
+
+/*
+ *        No domain
+ *
+ *   P1-.               P1 -> P2 : allow
+ *       \              P2 -> P1 : allow
+ *        'P2
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, without_domain) {
+	/* clang-format on */
+	.domain_both = false,
+	.domain_parent = false,
+	.domain_child = false,
+};
+
+/*
+ *        Child domain
+ *
+ *   P1--.              P1 -> P2 : allow
+ *        \             P2 -> P1 : deny
+ *        .'-----.
+ *        |  P2  |
+ *        '------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, child_domain) {
+	/* clang-format on */
+	.domain_both = false,
+	.domain_parent = false,
+	.domain_child = true,
+};
+
+/*
+ *        Parent domain
+ * .------.
+ * |  P1  --.           P1 -> P2 : deny
+ * '------'  \          P2 -> P1 : allow
+ *            '
+ *            P2
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, parent_domain) {
+	/* clang-format on */
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/*
+ *        Parent + child domain (siblings)
+ * .------.
+ * |  P1  ---.          P1 -> P2 : deny
+ * '------'   \         P2 -> P1 : deny
+ *         .---'--.
+ *         |  P2  |
+ *         '------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, sibling_domain) {
+	/* clang-format on */
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/*
+ *         Same domain (inherited)
+ * .-------------.
+ * | P1----.     |      P1 -> P2 : allow
+ * |        \    |      P2 -> P1 : allow
+ * |         '   |
+ * |         P2  |
+ * '-------------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, inherited_domain) {
+	/* clang-format on */
+	.domain_both = true,
+	.domain_parent = false,
+	.domain_child = false,
+};
+
+/*
+ *         Inherited + child domain
+ * .-----------------.
+ * |  P1----.        |  P1 -> P2 : allow
+ * |         \       |  P2 -> P1 : deny
+ * |        .-'----. |
+ * |        |  P2  | |
+ * |        '------' |
+ * '-----------------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, nested_domain) {
+	/* clang-format on */
+	.domain_both = true,
+	.domain_parent = false,
+	.domain_child = true,
+};
+
+/*
+ *         Inherited + parent domain
+ * .-----------------.
+ * |.------.         |  P1 -> P2 : deny
+ * ||  P1  ----.     |  P2 -> P1 : allow
+ * |'------'    \    |
+ * |             '   |
+ * |             P2  |
+ * '-----------------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, nested_and_parent_domain) {
+	/* clang-format on */
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/*
+ *         Inherited + parent and child domain (siblings)
+ * .-----------------.
+ * | .------.        |  P1 -> P2 : deny
+ * | |  P1  .        |  P2 -> P1 : deny
+ * | '------'\       |
+ * |          \      |
+ * |        .--'---. |
+ * |        |  P2  | |
+ * |        '------' |
+ * '-----------------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_domains, forked_domains) {
+	/* clang-format on */
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};

tools/testing/selftests/landlock/scoped_common.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Landlock scope test helpers
+ *
+ * Copyright © 2024 Tahera Fahimi <[e-mail]>
+ */
+
+#define _GNU_SOURCE
+
+#include <sys/types.h>
+
+static void create_scoped_domain(struct __test_metadata *const _metadata,
+				 const __u16 scope)
+{
+	int ruleset_fd;
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.scoped = scope,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd)
+	{
+		TH_LOG("Failed to create a ruleset: %s", strerror(errno));
+	}
+	enforce_ruleset(_metadata, ruleset_fd);
+	EXPECT_EQ(0, close(ruleset_fd));
+}

tools/testing/selftests/landlock/scoped_multiple_domain_variants.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Landlock variants for three processes with various domains.
+ *
+ * Copyright © 2024 Tahera Fahimi <[e-mail]>
+ */
+
+enum sandbox_type {
+	NO_SANDBOX,
+	SCOPE_SANDBOX,
+	/* Any other type of sandboxing domain */
+	OTHER_SANDBOX,
+};
+
+/* clang-format on */
+FIXTURE_VARIANT(scoped_vs_unscoped)
+{
+	const int domain_all;
+	const int domain_parent;
+	const int domain_children;
+	const int domain_child;
+	const int domain_grand_child;
+};
+
+/*
+ * .-----------------.
+ * |         ####### |  P3 -> P2 : allow
+ * |   P1----# P2  # |  P3 -> P1 : deny
+ * |         #  |  # |
+ * |         # P3  # |
+ * |         ####### |
+ * '-----------------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, deny_scoped) {
+	.domain_all = OTHER_SANDBOX,
+	.domain_parent = NO_SANDBOX,
+	.domain_children = SCOPE_SANDBOX,
+	.domain_child = NO_SANDBOX,
+	.domain_grand_child = NO_SANDBOX,
+	/* clang-format on */
+};
+
+/*
+ * ###################
+ * #         ####### #  P3 -> P2 : allow
+ * #   P1----# P2  # #  P3 -> P1 : deny
+ * #         #  |  # #
+ * #         # P3  # #
+ * #         ####### #
+ * ###################
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, all_scoped) {
+	.domain_all = SCOPE_SANDBOX,
+	.domain_parent = NO_SANDBOX,
+	.domain_children = SCOPE_SANDBOX,
+	.domain_child = NO_SANDBOX,
+	.domain_grand_child = NO_SANDBOX,
+	/* clang-format on */
+};
+
+/*
+ * .-----------------.
+ * |         .-----. |  P3 -> P2 : allow
+ * |   P1----| P2  | |  P3 -> P1 : allow
+ * |         |     | |
+ * |         | P3  | |
+ * |         '-----' |
+ * '-----------------'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, allow_with_other_domain) {
+	.domain_all = OTHER_SANDBOX,
+	.domain_parent = NO_SANDBOX,
+	.domain_children = OTHER_SANDBOX,
+	.domain_child = NO_SANDBOX,
+	.domain_grand_child = NO_SANDBOX,
+	/* clang-format on */
+};
+
+/*
+ *  .----.    ######   P3 -> P2 : allow
+ *  | P1 |----# P2 #   P3 -> P1 : allow
+ *  '----'    ######
+ *              |
+ *              P3
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, allow_with_one_domain) {
+	.domain_all = NO_SANDBOX,
+	.domain_parent = OTHER_SANDBOX,
+	.domain_children = NO_SANDBOX,
+	.domain_child = SCOPE_SANDBOX,
+	.domain_grand_child = NO_SANDBOX,
+	/* clang-format on */
+};
+
+/*
+ *  ######    .-----.   P3 -> P2 : allow
+ *  # P1 #----| P2  |   P3 -> P1 : allow
+ *  ######    '-----'
+ *              |
+ *              P3
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, allow_with_grand_parent_scoped) {
+	.domain_all = NO_SANDBOX,
+	.domain_parent = SCOPE_SANDBOX,
+	.domain_children = NO_SANDBOX,
+	.domain_child = OTHER_SANDBOX,
+	.domain_grand_child = NO_SANDBOX,
+	/* clang-format on */
+};
+
+/*
+ *  ######    ######   P3 -> P2 : allow
+ *  # P1 #----# P2 #   P3 -> P1 : allow
+ *  ######    ######
+ *               |
+ *             .----.
+ *             | P3 |
+ *             '----'
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, allow_with_parents_domain) {
+	.domain_all = NO_SANDBOX,
+	.domain_parent = SCOPE_SANDBOX,
+	.domain_children = NO_SANDBOX,
+	.domain_child = SCOPE_SANDBOX,
+	.domain_grand_child = NO_SANDBOX,
+	/* clang-format on */
+};
+
+/*
+ *  ######		P3 -> P2 : deny
+ *  # P1 #----P2	P3 -> P1 : deny
+ *  ######     |
+ *	       |
+ *	     ######
+ *           # P3 #
+ *           ######
+ */
+/* clang-format off */
+FIXTURE_VARIANT_ADD(scoped_vs_unscoped, deny_with_self_and_grandparent_domain) {
+	.domain_all = NO_SANDBOX,
+	.domain_parent = SCOPE_SANDBOX,
+	.domain_children = NO_SANDBOX,
+	.domain_child = NO_SANDBOX,
+	.domain_grand_child = SCOPE_SANDBOX,
+	/* clang-format on */
+};